Transistors are a bulwark of electronic switching and memory applications due to their extreme reliability and high ON/OFF ratios of 104-105. Transistors are three-terminal devices that include source, drain, and gate electrode terminals. Corresponding two-terminal electronic devices, having a source and a drain, typically have ON/OFF ratios that are orders of magnitude smaller than transistors. Two-terminal electronic devices can be operable in switching and memory applications, provided the devices display a non-linear current-versus-voltage response and have a great enough and reliable ON/OFF ratio.
Molecular-based devices and one-dimensional carbon nanostructures having non-linear current-versus-voltage response and current peak-to-valley ratios (PVRs) generally on the order of 2 to 100 have been reported. Likewise, two-terminal memory devices have been described that are based upon metal filamentary mechanisms. These include molecular-spaced devices, nanowire crossbar memories, and resistive random access memories using transition metal oxides. Coaxial multi-layer nanocables, which may include various materials, including carbon nanotubes, are of potential interest in molecular-based devices, since nanocables retain the one-dimensional features of both nanowires and nanotubes in the axial direction and form a heterojunction in the radial direction.
In view of the foregoing, development of electronic devices exhibiting nonlinear current-versus-voltage response, further characterized by a negative differential resistance region, and having high and reliable ON/OFF ratios characterized by large current PVRs would be of substantial benefit. Such devices may have applications in electronic switching, memory, and sensor applications. In memory applications, devices having stable, re-writable, non-volatile, and non-destructive read memories with fast switching times would be of substantial benefit in countless electronics applications where computer memory is used.